I'm currently not working with any private lender and my bank is going to take longer than the august 6th deadline. currently feeling a little stock, seller will not extend the contract.

You have made some pretty accurate predictions!  

Stocks are out of my control.

They too have different grades, ranging from in-stock ready to install (lower end) to quick ship (mid tier) and custom (high end - for HD / lowes of course).

I only look deeper into properties I could afford which is a small percentage.I understand some large companies are putting derivatives from rent on these properties into the stock market and that pension plans buy heavily into them.

My hope is to use about 300K as down payments for rentals (I have the rest diversified in stocks etc).

Real estate interests me because I feel like I've already done all I can (conservatively) with traditional investing (stock market, bonds, etc.) for now and I'd like to pay myself for housing instead of other people while I go to school. 

A little background information of myself:1.)I just recently graduated from high school as an honor student who is working as an assistant manager/receptionist at a real estate firm.  2.)I have grown up participating in 6 sports(possibly irrelevant to this topic but hopefully providing you guys an impression/idea of me as well). 3.)As stated in the post subject, I am an 18 year old. 4.)I come from a family of self-employed business owners, doctors, engineers, and stock investor(s).5.)I'm quite the tech-savvy person 6.)I will be taking 13 credits of college courses at a community college in the fall semester I under this career demands a great deal of one's time but I am willing to sacrifice that time for this career by limiting my social outings.

I dont have much interest in putting any money into the stock market maybe a small amount(im meeting with a financial advisor next week).

Home Depots stuff is lesser quality then your plumbing shop will stock.